Scale and change certain measurements of 3D image that was imported as .svg file
Frustrated at the way you ask your question ... I created a question back to you.

You will need to describe your application. As in how you intend to use this. I am starting to think that you are a marine bio-scientist who wants to keep a record of all the whales you come across visually? So you need to manipulate the image according to the sizes of the fish? Will the eventual image be just a flat image? Or will your eventual result you need be like Exhibit B. Which is a 3d model of the actual whale? In your previous posting you said you may want to know the surface area of the creature? All very confusing.

First and foremost please let us know your real intended application.

Secondly, Look at the image below. And tell us.



A. You want to import an image accurately into blender?
B. You want to create a 3d model of the whale?
C. You want to do both?
D. We don't understand and misinterpreted your question?

Some Ligo reference, a 3d artist may misunderstand what you really need to do ...
Realistic 3d image - A flat 2D image orthographic or perspective rendered/output from a 3d software.
2D image into a 3D image - Essentially placing a 2D image on a 3D polygonal plane. Like Exhibit A. 
Image Proper Measurement - Image Aspect ratio, so that the image doesn't look out of portion or stretched.